The study found that in every one of the 25 largest California counties, Blacks are arrested for marijuana possession at double, triple, or even quadruple the rate of Whites; however, U.S. Government studies have consistently found that young Blacks use marijuana at lower rates than young Whites. These racially biased arrests are system-wide, occurring in every county and nearly every police jurisdiction in California. This suggests that the pattern of over-representation of Blacks in arrests for marijuana possession is not due to the bias of individual officers, but rather to a general policy of resource allocation among law enforcement agencies. These marijuana possession arrests have serious consequences. They create permanent "drug arrest" records that can be easily found on the Internet by employers, landlords, schools, credit agencies, licensing boards, and banks. The stigma of a criminal record for marijuana possession can create barriers to employment and education for anyone; however, criminal records for marijuana possession severely limit the chances for employment and related economic advancement among the poor and the young, particularly young Blacks and Latinos. 10 figures and an appended table of marijuana possession arrest percentages in the 25 largest California counties (averages for 2004-2008)